Some guys have gutted the secondary cat. Not much power to be gained but its free if you do it yourself or very cheap if a shop does it. Gutting the secondary cat has no effect on you passing smog, readiness, or leaving a bad smell (once the primaries are warmed up) as there is no sensor behind it unlike the primary cat.

Do not do it like this guy with crappy crush bent piping. The BMW parts are specially designed and hydroformed to allow for enough clearance without significantly narrowing, crush bends are significant restrictions. Hydroformed bends like the stock pipes are NOT crush bends.

Do not do it like this guy with crappy crush bent piping. The BMW parts are specially designed and hydroformed to allow for enough clearance without significantly narrowing, crush bends are significant restrictions. Hydroformed bends like the stock pipes are NOT crush bends.

Once again Kit..tell us how you really feel I agree...TTPs are only $400.00.

OP's talking about passing SMOG tests and everyone is recommending getting rid of his cats. What am I missing?

No kidding people.

Without going with a catless set up, best bang for buck is R&P (higher numerical gearing) and a tune. Only a modest power increase with the tune, but the gearing change will allow for quicker acceleration in every gear. Coupled together (gearing + tune), you will feel a significant "seat of your pants" improvement.